This invention relates to an additive dispensing filter apparatus and to a method for dispensing an additive to a liquid.
It is known that operating liquids can be conditioned through filters so that the liquid system is protected from wear and damage. This is accomplished by removing particles, in particular particles that are relevant for wear, from the liquid system by filtration. It is also known that special chemical substances may be added to a filter for continuous oil care. In contact with the liquid to be filtered, the chemical substances (additives) are dissolved and in doing so release their active ingredients. These active ingredients fulfill the following functions: they protect the oil from thickening, from an increase in viscosity due to oxidation; they improve the lubricant properties of moving parts, dissolving deposits, dispersing foreign substances, providing protection against wear and improved flow properties. These additives may be accommodated anywhere in the filter system. In principle, the known approaches include those in which the additive is released only when a sheathing or covering part has dissolved away or the additives used have foreign substances such as polytetrafluoroethylene (e.g., PTFE or Teflon™) added to them.
U.S. Pat. No. 4,265,748 describes a liquid filter for an internal combustion engine, where an additive is arranged in a container within the filter, the container being closed by a diaphragm which dissolves on coming in contact with hot oil.
U.S. Pat. No. 4,066,559 describes additives embedded in polymers which dissolve at predetermined engine temperatures.
U.S. Pat. No. 4,014,794 proposes an oil filter which uses oil-soluble solid polymers which decompose slowly in oil and thereby act as viscosity modifiers. In addition, other additives may also be embedded in the polymer.
U.S. Pat. No. 5,209,842 describes an oil filter cartridge for an internal combustion engine, in which an additive in the form of solid PTFE particles is arranged inside the cartridge, where the particles break up on coming in contact with the hot oil and are transferred to the oil circulation through the filter element.
One disadvantage of these approaches is that the additive is not released until a sheathing or covering part has been dissolved or inert vehicle substances such as polymers are used or foreign substances such as PTFE are added. One problem here is that substances whose effects on the oil circulation are not absolutely known are being added to the oil circulation. Other approaches consist of using complex mechanical systems such as special types of encapsulation, perforated jacketing, special injectors and/or separate rooms that are to be acquired in addition are used. Examples of this are cited in U.S. Pat. No. 5,718,258. One disadvantage here is the high and very cost-intensive design complexity to achieve effective addition of an additive to the liquid circulation.